[43] CEPHALOPODS OF NORTHEASTERN COAST OF AMERICA. 253 



area within it is narrower and more deeply excavated, especially at the 

 base of the notch, where the excavation goes considerably lower than 

 the inner margin. The notch is narrower and not so much rounded at 

 its bottom. The tooth is about the same in size as that of No. 10, and 

 appears to be even more prominent, because the anterior edge of the 

 ala is more concave at its outer base ; it is also more compressed and 

 less regularly rounded at summit. This jaw measures 32.5 mm (1.30 inches) 

 from the tip to the posterior ventral border of mentum ; 17 mm from the> 

 tip to the bottom of the notch ; 4 mm from bottom of notch to the tip of the 

 tooth. 



Both these lower jaws agree in having a very prominent tooth on the 

 alar edge, with a large and deeply excavated notch between it and the 

 cutting edge of the beak, and in this respect differ from the lower jaw 

 of A. Harvey i, for in the latter the tooth or lobe is broad and less promi- 

 nent, while the notch is narrower and shallower. This seems to be the 

 best character for distinguishing the jaws of the two species. But they 

 also differ in the angle between the alar edge and the cutting edge of 

 the rostrum, especially of the lower jaw, for while in A. Harvey i this is 

 hardly more than a right angle, in A. princeps it is about 110°. More- 

 over, the darker color and firmer texture of the jaws of the latter seem 

 to be characteristic. 



To this species I have referred the Oatalina specimen (No. 14, p. 13), 

 preserved in the New York Aquarium. The jaws of the latter, which 

 were examined and carefully measured by me, agree very closely, both 

 in form and size, with those of No. 10, the type of the species, but are a 

 trifle larger. The total length of the upper mandible is 133 m '" ; greatest 

 breadth, 99 mm ; from inner angle of anterior edge to the dorsal end of 

 frontal lamina, 95 mm ; tip of rostrum, or beak, to the dorsal end of frontal 

 lamina, 92 mm ; tip of rostrum to bottom of notch, 19 mra ; notch to inner end 

 of anterior edge, 38"™; transverse breadth between anterior edges, 17" ,m . 



The total length of the lower mandible is 95 mra ; breadth from gular 

 lamina to inner end of ala?, 99 mm ; front edge of jaw to posterior end of 

 gular lamina, 83 mm ; breadth of ala?, 41""" ; posterior edge of ala? to end 

 of gular lamina, 44.5 mm ; tip of beak to bottom of notch, 22 mm ; notch to 

 inner angle of ala?, 70 mm ; depth of notch, 3.5 mni . 



The general form of this species is very w T ell shown on Plate VIII. 

 This figure has been made from the sketches and measurements made 

 by me soon after the specimen was received in New York and before it 

 had been "mounted'' (see p. 13). The head was, however, so badly in- 

 jured that it could not be accurately figured, and this part is, therefore, 

 to be regarded as a restoration, as nearly correct as could be made under 

 the circumstances. It may require considerable corrections, both as to 

 size and form. The caudal fin is remarkable for its small size, as in A. 

 Harvey i. Its breadth is scarcely more than that of the greatest diameter 

 of the body. It is short- sagittate in form, with strongly divergent side 

 lobes, which extend forward beyond their lateral insertions, and end in 



